The present invention relates to a light-reflective material used as a light-reflection member in a backlight of various display devices such as a liquid crystal display, illuminated signboard, lighting equipment and so forth, and it relates to a light-source device using the same.
Conventionally, a flat light source that lights from the back face of a signboard, a display board or the like, includes a plurality of rod-like light sources such as fluorescent lamps and a diffusion board, a diffusion sheet or a diffusion material formed of a combination thereof is disposed on the front face of the light source, and a light-reflective material is disposed in the back of the light source. In addition to such a backlight called a direct type, flat light sources include an edge-light type backlight, in which a lamp such as a cold-cathode tube is disposed at an end portion of a transparent plate called a light guide plate, and which is used for multiple purposes such as liquid crystal displays and the like. In these flat light sources, a light-reflective material is wrapped partially around the lamp or disposed on a surface opposite the light-emitting surface of the light guide plate. As the light-reflective material for flat light sources, a white plastic film is used in which a white pigment is mixed in a synthetic resin or in which a multiplicity of fine holes are formed in the synthetic resin sheet.
In order to increase brightness of the flat light source, attempts have been made to increase the light reflectance of the aforementioned light-reflective material, to increase the brightness of a light source such as a fluorescent light and to increase transmittance of a diffusion material or the like. As a method of increasing the light reflectance of the light-reflective material, stacking a plurality of white plastic films and increasing the thickness of the film itself are approaches that have been employed.
However, when films are stacked to increase the light reflectance, the number of components of the flat light source is increased. Therefore, a problem arises that excessive labor is required for each component when the light-reflective material is processed into an appropriate shape as required or wound about a lamp, for example. On the other hand, the method involving increasing the thickness of the film itself to increase the light reflectance is also undesirable since flexibility may be reduced when the light-reflective material is processed into an appropriate shape as required or wound about a lamp. Further, although its cause is not clear, when the thickness of the film itself is increased to increase the light reflectance, the amount of increase in the light reflectance is lower than when the films are stacked to increase the light reflectance, even though materials of the white plastic film and the total thicknesses are the same.